Sir David Attenborough, Sir Richard Branson and Dame Maggie Smith are among 200 public figures urging newspaper bosses to accept a new press regulator underpinned by Royal Charter.

The leading names in arts, film, science and human rights have joined victims of press abuse to give their support to the Hacked Off campaign for tighter press regulation.

The list of signatures appears in an advert published in a number of newspapers today - a year after the publication of the draft Royal Charter on press regulation.

The advert asks: "What do all these people have in common? The Leveson Royal Charter Declaration."

It says the press has "nothing to lose and can only be enhanced" by agreeing to the move.

The draft Royal Charter was sealed by the Queen in October, but editors have so far refused to sign up.

Instead industry leaders have come up with the Independent Press Standards Organisation (Ipso), with more than 90% of publications in the UK said to be in alignment.

The new press standards body will replace the current Press Complaints Commission (PCC) and is ready to begin operations on May 1.

Comedian John Cleese, whose name appears in the advert, said: "The big newspaper bosses are lying though their teeth about the Leveson recommendations.

"They say their freedom is being threatened, but when anyone points out what self-serving rubbish this is, they ignore these arguments and instead attack the people who are trying to get the truth heard. Their unscrupulousness is breath-taking."

Writer Ian McEwan said: "Freedom of expression is not the freedom to bully, to intimidate, to intrude where there is no public interest, or to corrupt public bodies with secret bungs.

"Leveson, rather like a good, hard-working journalist, exposed many such abuses in the press. The abusers, who are a mighty and self-interested faction, prefer business as usual.

"But those who value free-thinking and open political process know that bullies and corruptors must be held to account. We urgently need wise and plausible regulation."